Cable television systems typically route television signals to subscriber premises over a variety of different communication media, such as fiber optic cables and coaxial cables. FIG. 1 illustrates a conventional cable television system 100, which includes a head end section 105 that receives satellite signals and demodulates the signals to baseband. The baseband signal is then transmitted over a communication medium after conversion to an optical signal or a radio frequency (RF) signal. Because the signal can be transmitted for relatively long distances, one or more distribution amplifiers 110 are provided for boosting the signal. Taps 120, 125, 130 are situated along the communication media to tap off signals to subscriber premises 135.
As shown in FIG. 1, a distribution amplifier 110 can have multiple outputs, as may be better understood by referring to FIG. 2, which is a block diagram of a conventional distribution amplifier 110. The amplifier 110 typically includes an RF input 140 that couples the signal to an output gain stage section 142 comprising one or more active amplifier circuits 144, 146, 148 for outputting a main output signal and one or more auxiliary output signals. The main output signal is provided to an automatic gain control (AGC) circuit 156 for modifying the input 140 to regulate the gain of the output gain stage section 142 in a conventional manner. The main output signal and the auxiliary output signals, e.g., aux1 and aux2, are provided at outputs 162, 164, 166 and routed to taps, such as taps 120, 125, 130, and other devices, such as other active amplifiers, within the cable system 100.
Distribution systems often include a large number of devices, each of which can include a large amount of circuitry, and the devices are usually located remotely from the head end section of the cable system. Therefore, failure of system devices and components, such as components within an amplifier, can go undetected, resulting in unacceptable signal levels or interrupted service at the subscriber premises. Some typical amplifiers include a status monitoring transponder to attempt to rectify this problem. However, conventional status monitors only monitor the voltage level of the AGC pilot carrier circuit, and the AGC circuit is coupled only to the main output.
Consequently, problems in active amplifier sections that provide auxiliary outputs are not detected.
Thus, what is needed is a better way to monitor the status of a devices and stages included in a cable television system.